[PATCH v2] setsourcefilter: Use malloc() rather than alloca().

[Joe Simmons-Talbott <josimmon@redhat.com>]

To prevent possible stack overflow use malloc() rather than alloca().
---
Changes to v1:
  - don't save and restore errno around free()

 sysdeps/unix/sysv/linux/setsourcefilter.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/setsourcefilter.c b/sysdeps/unix/sysv/linux/setsourcefilter.c
index 538f4de696..2823168d34 100644
--- a/sysdeps/unix/sysv/linux/setsourcefilter.c
+++ b/sysdeps/unix/sysv/linux/setsourcefilter.c
@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <alloca.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
@@ -34,17 +33,11 @@ setsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
   /* We have to create an struct ip_msfilter object which we can pass
      to the kernel.  */
   size_t needed = GROUP_FILTER_SIZE (numsrc);
-  int use_alloca = __libc_use_alloca (needed);
 
   struct group_filter *gf;
-  if (use_alloca)
-    gf = (struct group_filter *) alloca (needed);
-  else
-    {
-      gf = (struct group_filter *) malloc (needed);
-      if (gf == NULL)
-	return -1;
-    }
+  gf = (struct group_filter *) malloc (needed);
+  if (gf == NULL)
+    return -1;
 
   gf->gf_interface = interface;
   memcpy (&gf->gf_group, group, grouplen);
@@ -63,12 +56,7 @@ setsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
   else
     result = __setsockopt (s, sol, MCAST_MSFILTER, gf, needed);
 
-  if (! use_alloca)
-    {
-      int save_errno = errno;
-      free (gf);
-      __set_errno (save_errno);
-    }
+  free (gf);
 
   return result;
 }
-- 
2.39.2